A conventional ring cone type stepless transmission is disclosed in Jananese Patent Publication No. 62-270858, for example. This transmission comprises taper cones, a carrier relatively rotatably supporting shaft, a ring-shaped change connected to an input shaft, a ring-shaped change speed member for contacting the taper cones, and an internal gear for receiving torque from the taper cones. The ratio between the rotating speed transmitted to the carrier and the rotating speed output from the internal gear is steplessly changed by variations in the position of contact between the taper cones and change speed member.
More particularly, the taper cones are oscillatable supported by the carrier through oscillatable axes, to secure a suitable contact pressure between the taper cones and change speed member. The shaft that drives the carrier supports a limiting member in contact with the taper cones to stop oscillations of the taper cones away from the change speed member.
According to this construction, however, when the position of the change speed member is adjusted, an increased difference is produced between the pressure applied by the change speed member to the taper cones and the pressure applied by the limiting member to the taper cones. Consequently, the taper cones may be subjected to a moment whose center is displaced from the respective oscillatable axes. Further, the oscillatable axes must be strong for the above reason and because through these oscillatable axes power is transmitted from the carrier to the taper cones. The transmission line in this known construction tends to be complicated since a gear is required for taking out torque of the taper cones.